mirror of https://github.com/espruino/BangleApps
77 lines
2.3 KiB
Markdown
77 lines
2.3 KiB
Markdown
# Espruino Flag Raiser
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An app to send a command to another Espruino to cause it to raise a flag.
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For this to work, you need to upload the following code to another
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bluetooth Espruino device (the one with the flag attached) :
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```
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var FLAG_PIN = D14;
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var s = require("servo").connect(FLAG_PIN);
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s.move(1,3000); // move to position 1 over 3 seconds
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var timeout;
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function flag() {
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if (timeout) clearTimeout();
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s.move(0.2,2000);
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timeout = setTimeout(function() {
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timeout = undefined;
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s.move(1,2000);
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},2000);
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}
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setWatch(flag, BTN, {repeat:true});
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NRF.setServices({
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"3e440001-f5bb-357d-719d-179272e4d4d9": {
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"3e440002-f5bb-357d-719d-179272e4d4d9": {
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value : [0],
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maxLen : 1,
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writable : true,
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onWrite : function(evt) {
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flag();
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}
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}
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}
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}, { uart : false });
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NRF.setAdvertising({}, {name:"Flag"});
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```
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## Wiring
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This is designed for an [MDBT42Q Breakout board](http://www.espruino.com/MDBT42Q)
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but should work on any Bluetooth LE Espruino device - you just need to change `FLAG_PIN`
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to the name of the pin that's connected to the servo motor.
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However, as designed:
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* Get an [MDBT42Q Breakout board](http://www.espruino.com/MDBT42Q)
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* Connect `GND` to GND (black) of a 3.7v LiPo battery
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* Connect `Vin` to positive (red) of the battery
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* Take a servo motor and:
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* Connect the Black wire to `GND` (LiPo GND)
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* Connect the Red wire to `Vin` (LiPo 3.7v)
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* Connect the White wire to `D14` on the MDBT42Q
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## How does it work?
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The code above changes the advertised name of the Espruino device to be
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`Flag` (which the app then searches for).
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Then, it adds a service UUID `3e440001-f5bb-357d-719d-179272e4d4d9` (this
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is just a random number we made up) with characteristic `3e440002-f5bb-357d-719d-179272e4d4d9`
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(the same UUID with the second 16 bits incremented). When the characteristic
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is written (with any data), `flag()` is called, which raises the flag.
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`flag()` itself uses the [servo module](http://www.espruino.com/Servo+Motors)
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to allow the servo motor to be controlled easily.
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You might find the [Espruino About Bluetooth LE page](http://www.espruino.com/About+Bluetooth+LE)
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is useful as an introduction to services and characteristics.
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### Don't want to use a servo motor?
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No problem, just replace `flag()` with a function that controls whatever you need
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it to.
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